This application is not related to any pending United States or international patent application.
This application is not referenced in any Microfiche Appendix.
Explosion detonators are used whenever it is required to initiate or set off an explosive charge. Explosives may be in the form of solids, liquids or powders and are typically set-off either by heat or shock or a combination of heat and shock. A common initiated explosion is that which takes place in a shell, whether a rifle or shotgun shell, in which a detonation actuates an explosive that propels a projectile or projectiles, such as a lead slug or lead shot, out the muzzle of a gun. Other types of detonators are used to set off explosives used in mining and construction, such as dynamite, nitroglycerin and many other types of more modern explosive compositions. Military equipment including cannons, howitzers and so forth frequently function by loading bags of explosive into the breach of a gun barrel that has a projectile therein and detonating the explosive after the breach is closed to expel the projectile at high velocity.
For background information relating to explosion detonators, reference may be had to the following previously issued United States patents:
The invention herein relates specifically to an explosion detonator that is particularly useful in firing relatively small explosive charges such as the type of charge frequently found in shotgun shells that may typically vary in size from 410 gauge to 8 gauge industrial. The invention herein is also particularly applicable for firing shells that are not intended to be utilized as ammunition in a weapon but are intended for industrial purposes, such as 8 gauge industrial shells.
Shotgun size shells are frequently utilized in geophysical mapping.
For background information relating to the use of small explosives of the shotgun shell size in geophysical mapping reference may be had to U.S. Pat. No. 4,867,266 entitled, xe2x80x9cSeismic Energy Sourcexe2x80x9d that issued on Sep. 19, 1989. Another example of the use of shotgun size shells in a seismic system may be found in U.S. Pat. No. 4,324,310 entitled, xe2x80x9cSeismic Apparatusxe2x80x9d that issued Apr. 13, 1982. An even earlier example of the use of small size explosives, such as shotgun shells, for scientific exploration is revealed in U.S. Pat. No. 4,223,759 entitled, xe2x80x9cLow Energy Source for Seismic Operationxe2x80x9d that issued on Sep. 23, 1980.
When seismic exploration is conducted using small explosive charges such as the size approximated by shotgun shells, it is important that an electric actuated explosive detonator be available that is highly dependable, inexpensive, safe to handle and electrically initiated. Many types of small explosives such as shotgun shells and particularly the shotgun shells utilized for hunting and other recreational activities employ a primer cap that is initiated by physical detonationxe2x80x94that is, a pin strikes and deforms a percussion primer cap to initiate the explosion of the charge that propels projectiles from the barrel of a gun. In seismic exploration it is much preferred that the ignition of explosive charges be accomplished electrically rather than physically since the physical action of a mechanism may introduce erratic firing times that complicate the energy pattern generated by the explosive charge, especially multiple charges that must be fired simultaneously. It is, therefore an object of this invention to provide an electric actuated explosive detonator that meets all of the requirements above mentioned for detonators, particularly for detonators used for seismic exploration, by providing a detonator that is inexpensive, highly dependable, and easily adaptable for use in portable equipment.
The present invention provides an electric actuated explosion detonator that includes a confined explosive charge capable of being detonated by heat and/or shock. A carbon film electric resistor is positioned in engagement with the confined electric charge. The carbon film resistor has two electrical contacts and has a predetermined electric current carrying capability and is subject to receiving, by the application of an electrical source of sufficient voltage and wattage an instantaneous current flow to cause the carbon film resistor""s immediate disintegration.
A carbon film electric resistor adaptable for use in this invention may, and preferably is, of the readily commercially available type of carbon film resistors as characteristically employed in electric and electronic circuitry. Such carbon film resistors are typically formed in the shape of a small diameter cylindrical device with electrodes on the opposed ends of the device. Most frequently the electrodes are in the form of two wires, one extending from each of the opposed ends of a cylindrical shaped carbon film resistor.
A typical electrical resistor that functions ideally in the practice of this invention may be of a size of about xc2xc watt and may be typically about 15 to 25 ohms and of the carbon film type. Such carbon film resistors are commonly available on the market at a cost of less than two or three cents each. In the practice of the invention, the confined explosive charge may typically be an explosive propellant of the type commonly used in manufacturing ammunition.
The explosive charge or propellant used in practice in the invention may be confined, as an example, within a shell cartridge. The shell cartridge may be of the type that has a metal head and a non-metallic casing. The metal head may typically be of the type that has a central opening through which the resistor may be positioned to be immersed within explosive powder packed within the shell casing.
In one embodiment of the invention, an electric actuated explosive detonator is in the form of a shell having a metal head portion having an opening therein and having a small tubular insulator received in the opening. One conductor wire from a carbon film resistor may extend through the tubular opening to be attached to a contact button that is received within the opening in the shell head portion.
While the resistor as used in this invention may be any kind of electrical resistor that has a maximum current carrying capability and that has conductors extending from it, the ideal commercially available resistor is the carbon film resistor.
A typical commercially available resistor that functions ideally in practicing the invention is a carbon-film resistor of about 20 ohms and xc2xc watt. The ohmage and wattage can vary up or down from these amounts but the objective of the invention is achieved only when a resistor of ohmage and wattage is used, according to the power source available, such that upon the application of a power source, either A/C or D/C to the resistor, it immediately disintegrates due to excess current flow that immediately exceeds the resistor""s wattage. A power supply that can be used to activate the explosive detonator of this invention can be of the type that produces 110/120 volts A/C that can be energized either from a readily available household current 110/120 volts A/C outlet or that can be obtained from an inverter that operates on 12 volts or similar battery. By the use of an inverter that uses a 12 volt or similar battery as an energy source to provide an elevated D/C or an elevated A/C output of approximately 110/120 volts, the explosion detonator can easily be used in field conditions and with equipment that is readily commercially available and exceedingly economical.
A better understanding of the invention will be obtained from the following detailed description of the preferred embodiments taken in conjunction with the attached drawings.